(CNN)Ted Cruz's campaign is opening the opposition research book on John Kasich, launching their first negative ad against him before the primary in Wisconsin.

In a new spot that began airing on Wisconsin television on Saturday, Cruz's campaign is taking aim at a company, Worthington Industries, and suggesting unsavory ties to the Ohio governor. The advertisement seems to reflect a strategic shift by Cruz's aides that Kasich poses some threat to Cruz in Wisconsin -- or that his voters are at least up for grabs.

The spot implies that Kasich awarded the company hundreds of thousands of dollars in tax breaks because they paid him money before he won the governorship -- which has not been proven. A state ethics panel in 2013 declined to investigate the potential conflict of interest, which was pushed by Kasich's eventual opponent for governor in 2014.

It does accurately point out that the Worthington Industries chief executive, John P. McConnell, has been a Kasich supporter and that the company fired some employees last year.

"The company laid off 100 Ohioans even as the CEO cut a half-million dollar check to Kasich's super PAC," the spot claims. "John Kasich's not for us."

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Kasich's chief strategist, John Weaver, said the governor had no say over who received tax credits -- and intensified the escalating clash by referencing what Weaver said Cruz's own ethical red flag.

"Ted Cruz is recycling failed Democrat attacks in a desperate effort to smear Gov. Kasich. It didn't work for dishonest Ohio Democrats in 2014 and won't work for deceptive Ted Cruz now," Weaver said in a statement.

Ever since Kasich became a serious obstacle to Cruz's strategy, by winning Ohio on March 15, the Texas senator and his aides have been slow to go negative on him. Cruz himself at one point declined to even judge whether Kasich was a "conservative." Last week though, Cruz's super PAC began airing negative spots against him in Wisconsin, where he solidly trails both Cruz and GOP presidential front-runner Donald Trump ahead Tuesday's primary.

Cruz's campaign is also now offering its first scrutiny of Kasich's policy record as governor. Cruz recently sent some Wisconsin voters two mail pieces attacking Kasich's record on government spending, and a separate one saying he "puts our military at risk," according to the literature sent to a voter in the state and obtained by CNN.

"John Kasich has the worst spending policy of any governor," reads one Wisconsin mailer, citing figures from the Cato Institute.

"Slashing defense," a bullet point on the second mailer reads. "Siding with liberals," goes another.